Self-centering ability of unbonded post-tensioned precast concrete shear walls has been attributed to the presence of post-tensioning force. However, the experimental results presented in this paper indicate that the post-tensioning force may completely die out during cyclic loading while the walls are able to retain their superior self-centering characteristic. Moreover, the analytical study presented in this article indicates that with proper configuration of end-anchorages for post-tensioned tendons, self-centering of post-tensioned walls can be achieved even when the post-tensioning force vanishes. This study also investigates the effects of tendon layout, tendon end-anchorage configuration, and external vertical load on the self-centering ability of unbonded precast concrete shear walls subjected to earthquake loading.

In 1963, a geometry-dependent approach to estimate the coefficient of restitution (COR) was proposed for free rocking structures. Since then, this estimation has been reported as being consistently lower than results obtained from experimental data. An assumption used by the original model is shown to be the cause of this underestimation. Identifying that the rocking takes place over a contact region, this study introduces a modified formulation for free rocking bodies and proposes an improved COR estimation to accurately quantify the energy dissipation of these structures. Using experimental data, it is shown that the improved CORs consistently provide better correlation to those established from tests than the COR obtained from the original approach.

Reported evidence suggests that failure of gusset plates initiated the collapse of the I-35W Bridge in Minneapolis, Minnesota. The particular gusset plates were at a panel point designated as U10. Therefore, an analytical investigation was conducted on the condition of the U10 gusset plates at the time of bridge collapse. The forces delivered to panel point U10 were reproduced using available information of the bridge. These forces were introduced to detailed nonlinear three-dimensional finite-element models to calculate stress and strain states of the gusset plates. The results indicate that substantial portions of the U10 gusset plates were yielded at the time of collapse, confirming earlier findings from federal and state investigations. Weight increase due to past deck reconstruction and construction material and equipment staged on the day of collapse, along with insufficient thickness of the gusset plate, were identified as the main contributing factors to the substantial yielding. The results also ...

Unlike the use of bonded reinforcement to anchor a masonry wall to its foundation, the use of unbonded posttensioning may result in a controlled rocking response of the wall. Considering that conventional analysis techniques routinely employed for monolithic structures are inadequate to describe a controlled rocking response, this paper introduces analysis methods that are able to predict the monotonic force-displacement responses of masonry walls with unbonded posttensioning. These methods include (1) an iterative procedure that employs sectional analysis and accounts for the confinement effects attributable to lateral friction at the wall-to-foundation interface and (2) a simplified procedure that is based on equivalent stress block analysis. The two methods are compared against experimental data from three past research studies, and high-fidelity finite-element models are used to verify predictions of the wall responses, including the neutral axis depth (NAD) at the wall-to-foundation interface. Comparisons show the proposed analysis methods to adequately capture the experimental force-displacement responses and produce NAD variations that agree well with the finite-element models.

Digital manufacturing has transformed many industries but has had only a limited impact in the construction sector. To capitalize on advanced manufacturing techniques, this paper introduces a radically new connection approach for gravity structural steel frames. The proposed intermeshed steel connection (ISC) exploits robotic abilities to cut structural steel member ends precisely to accelerate deployment and offer better disassembly options over existing approaches. Forces are transferred through common bearing surfaces at multiple contact points, and connections can be secured by small locking pieces. This paper introduces the geometry, manufacturing, and initial analysis and test results of the connection. The paper demonstrates the ability of the connection to (1) be manufactured within current industrial tolerances, (2) be erected and disassembled, and (3) perform at expected design levels.